CSS

Cascading Style Sheets, fondly referred to as CSS, is a simple design language intended to transform the presentation of a Web Pages as well as many ostensibly nonweb environments.

CSS handles the look and feel part of a web page. Using CSS, you can control the color of the text, the style of fonts, the spacing between paragraphs, how columns are sized and laid out, what background images or colors are used, layout designs,variations in display for different devices and screen sizes as well as a variety of other effects.

CSS is easy to learn and understand but it provides powerful control over the presentation of an HTML document. Most commonly, CSS is combined with the markup languages HTML or XHTML.

History of CSS

Cascading Style Sheets level 1 (CSS1) came out of W3C as a recommendation in December 1996. This version describes the CSS language as well as a simple visual formatting model for all the HTML tags.

CSS2 became a W3C recommendation in May 1998 and builds on top of CSS1. This version adds support for media-specific style sheets e.g. printers and aural devices, downloadable fonts, element positioning and tables.

CSS3 became a W3C recommendation in June 2012 and builds on older versions CSS. it has divided into documentations called as Modules and here each module having new extension features defined in CSS2.

CSS Syntax

A CSS comprises of style rules that are interpreted by the browser and then applied to the corresponding elements in your document. A style rule is made of three parts ?

• Selector ? A selector is an HTML tag at which a style will be applied. This could be any tag like <h1> or <table> etc.
• Property ? A property is a type of attribute of HTML tag. Put simply, all the HTML attributes are converted into CSS properties. They could be color, border etc.
• Value ? Values are assigned to properties. For example, color property can have value either red or #F1F1F1 etc.

You can put CSS Style Rule Syntax as follows ?

selector { property: value }
        

Example ? You can define a table border as follows ?

table{ border :1px solid #C00; }
        

Here table is a selector and border is a property and given value 1px solid #C00 is the value of that property.

You can define selectors in various simple ways based on your comfort. Let me put these selectors one by one.

The Type Selectors

This is the same selector we have seen above. Again, one more example to give a color to all level 1 headings ?

h1 {
   color: #36CFFF; 
}        

The Universal Selectors

Rather than selecting elements of a specific type, the universal selector quite simply matches the name of any element type ?

* { 
   color: #000000; 
}        

This rule renders the content of every element in our document in black.

The Descendant Selectors

Suppose you want to apply a style rule to a particular element only when it lies inside a particular element. As given in the following example, style rule will apply to <em> element only when it lies inside <ul> tag.

ul em {
   color: #000000; 
}        

The Class Selectors

You can define style rules based on the class attribute of the elements. All the elements having that class will be formatted according to the defined rule.

.black {
   color: #000000; 
}        

This rule renders the content in black for every element with class attribute set to black in our document. You can make it a bit more particular. For example ?

h1.black {
   color: #000000; 
}        

This rule renders the content in black for only <h1> elements with class attribute set to black.

You can apply more than one class selectors to given element. Consider the following example ?

<p class = "center bold">
   This para will be styled by the classes center and bold.
</p>        

The ID Selectors

You can define style rules based on the id attribute of the elements. All the elements having that id will be formatted according to the defined rule.

#black {
   color: #000000; 
}        

This rule renders the content in black for every element with id attribute set to black in our document. You can make it a bit more particular. For example ?

h1#black {
   color: #000000; 
}        

This rule renders the content in black for only <h1> elements with id attribute set to black.

The true power of id selectors is when they are used as the foundation for descendant selectors, For example ?

#black h2 {
   color: #000000; 
}        

In this example all level 2 headings will be displayed in black color when those headings will lie with in tags having id attribute set to black.

The Child Selectors

You have seen the descendant selectors. There is one more type of selector, which is very similar to descendants but have different functionality. Consider the following example ?

body > p {
   color: #000000; 
}        

This rule will render all the paragraphs in black if they are direct child of <body> element. Other paragraphs put inside other elements like <div> or <td> would not have any effect of this rule.

The Attribute Selectors

You can also apply styles to HTML elements with particular attributes. The style rule below will match all the input elements having a type attribute with a value of text ?

input[type = "text"] {
   color: #000000; 
}        

The advantage to this method is that the <input type = "submit" /> element is unaffected, and the color applied only to the desired text fields.

There are following rules applied to attribute selector.

• p[lang] ? Selects all paragraph elements with a lang attribute.
• p[lang="fr"] ? Selects all paragraph elements whose lang attribute has a value of exactly "fr".
• p[lang~="fr"] ? Selects all paragraph elements whose lang attribute contains the word "fr".
• p[lang|="en"] ? Selects all paragraph elements whose lang attribute contains values that are exactly "en", or begin with "en-".